Barack Obama has told Gordon Brown he hopes to "strengthen the transAtlantic relationship" if he wins his bid for the White House.

He insisted co-operation with the UK was crucial for dealing with climate change, terrorism, and the economy following talks with the Prime Minister at Downing Street.

After meeting the Illinois Senator, Mr Brown headed to Suffolk to start his summer holiday, with dissent within the Labour Party still ringing in his ears following the Glasgow East by-election defeat.

Mr Obama's visit to Britain marked the final leg of a whistle-stop tour of the Middle East and Europe.

Speaking on the steps of 10 Downing Street, Mr Obama said he and the Prime Minister had talked about how to strengthen the relationship between the two countries to tackle international issues jointly.

He also expressed gratitude for Britain's assistance on issues like Afghanistan.

Having both made recent trips to the Middle East they had plenty to discuss - not least troop withdrawal from Iraq. Mr Obama has consistently stated that he wants to get US troop's home from Iraq within 16 months of taking office.

Last weekend after meeting the top US commander in Iraq General David Pitraeus, he rowed back on that just slightly - tempering his declaration by saying that goal may have to be shifted back depending on events.

Before the meeting with Mr Brown, Mr Obama held breakfast talks with former Prime Minister Tony Blair, who is now a Middle East envoy.

Mr Blair's new role gave the two men a huge amount to talk about. Mr Obama has put the resolution of the Palestinian-Israeli question at the heart of his foreign policy - pledging to 'roll his sleeves up' from the moment he takes office.

Mr Obama's final handshake of the day was with Conservative leader David Cameron, who he met at the House of Commons before heading to the airport and home.

Mr Cameron and Mr Obama spent almost an hour talking - far longer than scheduled - before the US candidate left with a box of CDs by the Tory leader's favourite bands, including The Smiths, Radiohead, Gorillaz and Lily Allen.

Obama's Speech In Berlin

The Illinois senator has been away from home for a week now on a hectic tour which has taken him to Afghanistan, Iraq, Jordan, Israel, the Palestinian Territories, Germany, France and now the UK.

The Berlin rally - when more than 200,000 people turned out to hear him speak - is being seen as the showpiece event of the trip.

It provided sparkling pictures of Barack Obama enjoying the applause of an adoring German crowd - in turn soaking up his promises for a better, more sensitive America.

But in reality it was the Iraq/Afghanistan leg of the trip that was the most important for him politically.

Barack Obama's Republican critics have tried to paint him as a naïve pacifist who would get America into big trouble with his inexperience in foreign policy.

Those criticisms were almost goading Barack Obama to hit back with a trip to prove them wrong.

So being seen with the generals in Iraq - and looking like a commander-in-chief of the United States was a piece of imagery even more important than waving at the crowds in Berlin. And certainly one any picture taken in London is unlikely to eclipse.